Antarctic Peninsula models show emissions levels will shape ice, seas and wildlife
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The Antarctic Peninsula provides an early warning system for the southernmost continent when it comes to climate change. And the predictions are gloomy — but it is not yet too late to avoid irreversible changes, researchers report February 20 in Frontiers of environmental scienceThis.
In the new study, the team first documented how the peninsula is already transforming as the planet warms, then assessed how different levels of warming by 2100 could alter the fate of the peninsula, including its marine and terrestrial ecosystems, land and sea ice, ice shelves, and extreme weather events. These estimates of global warming – of 1.8, 3.6 and 4.4 degrees Celsius compared to pre-industrial times – are based on three different simulation scenarios of future greenhouse gas emissions.
“The Antarctic Peninsula is really the wake-up call for the continent,” says Bethan Davies, a glaciologist at the University of Newcastle in England. It is a relatively small part of the continent, but it is disproportionately visible due to fishing, tourism and scientific research.
“Changes that happen on the Antarctic Peninsula don’t stay on the Antarctic Peninsula either,” says Davies. Retreat of glaciers in the southern part of the peninsula may make West Antarctic glaciers more vulnerable to melting. The decrease in sea ice around the peninsula is increasing warming around the Southern Ocean more broadly. This, in turn, may slow the formation of a body of water known as the Antarctic Intermediate Water, which connects the Southern Ocean to global ocean circulation. Less sea ice also means less krill (Superb euphausia), tiny crustaceans at the base of the Southern Ocean food chain.
In 2019, with an average temperature on Earth around 1 degree Celsius above pre-industrial times, the The Antarctic Peninsula was already experiencing significant changes. Relatively warm circumpolar deep waters swirling near the peninsula accelerated melting; several huge chunks of ice had broken glaciers on the continent. But the nearby ocean food web, dependent on sea ice and krill, was still intact.
“Unfortunately, we are currently at around 1.4°C of warming,” says Davies. Limiting future warming to a maximum of 1.5°C has been aimed at a better scenario for the planet. In November, the United Nations Environment Program has declared that there is now no chance that the world will remain within this limit, while countries continue to fail to meet their own emissions reduction targets. “We were therefore motivated to examine the Antarctic Peninsula under several scenarios. »
In a best-case scenario of 1.8°C warming by 2100, the ocean food web would shrink as winter sea ice shrinks and ocean temperatures rise. Wildlife populations are beginning to shift: species less dependent on krill and sea ice, such as fur seals, elephant seals, and gentoo penguins (Pygoscelis Papua), become more abundant.
Moderately high greenhouse gas emissions, which could warm the planet by about 3.6 degrees Celsius by 2100, would significantly reduce sea ice concentration and warmer circumpolar deep waters would rise to eat away at the peninsula’s ice shelves. Extreme events, including oceanic heatwaves and atmospheric riverswould become both more serious and more frequent.
The worst-case scenario, with very high greenhouse gas emissions, would warm the planet by about 4.4 degrees Celsius compared to pre-industrial times by 2100. This significantly increases the impacts seen in the medium-high scenario, Davies says. Sea ice cover could decline by 20 percent, devastating krill-dependent species such as whales and penguins and warming ocean waters globally. The Larsen C ice floewhich lost a piece of ice the size of Delaware in 2017, would likely completely collapse by 2100. By 2300, the George VI Ice Shelf could collapse; this is currently helping to prevent inland ice from flowing out to sea. This could cause sea levels to rise by up to 116 millimeters.
What makes this situation very worrying is that many of these changes would be irreversible, at least on a human scale. “Once you start to recede glaciers, you trigger instability in the marine ice sheet, and that process is essentially irreversible. It’s very difficult to regrow these glaciers,” says Davies. Sea ice is also very difficult to recover once lost; Darker ocean waters absorb more heat from the sun, making it difficult to cool them enough to reform sea ice, she says.
“All of this illustrates what policymakers around the world should know: Every decision we make today to reduce carbon emissions makes the challenges of the future more manageable,” says Peter Neff, a glaciologist at the University of Minnesota in St. Paul, who is not an author of the new study.
“The Antarctic Peninsula has long been seen as the canary in the coal mine when it comes to the loss of the Antarctic ice sheet… where we’ve seen smaller versions of the ice shelf collapse that scientists fear for West Antarctica,” says Neff. West Antarctica, including the rapidly melting and intensively studied Thwaites Glacier, tends to occupy all the conversation about Antarctic change, Neff adds. This includes geoengineering solutions proposed to slow down this melting. “None of the proposed ‘solutions’ would help save the Antarctic Peninsula,” he says.
